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Climate Change

Overview of Greenhouse Gases

Emissions of Fluorinated Gases

photo of F-gas molecule
Properties of F-gases
Chemical Formula HFCs, PFCs, SF6
Lifetime in Atmosphere HFCs: 1-270 years
PFCs: 800-50,000 years
SF6: 3,200 years
Global Warming Potential (100-year) HFCs: 140-11,700
PFCs: 6,500-9,200
SF6: 23,900
U.S. Fluorinated Gas Emissions, By Source
Pie chart of U.S. fluorinated gas emissions by source. 89 percent is from the substitution of ozone depleting substances, 4 percent from electrical transmission and distribution, 3 percent from HCFC-22 production, 2 percent from production and processing of aluminum and magnesium, and 2 percent from semiconductor manufacture.

Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012.

Unlike many other greenhouse gases, fluorinated gases have no natural sources and only come from human-related activities. They are emitted through a variety of industrial processes such as aluminum and semiconductor manufacturing. Many fluorinated gases have very high global warming potentials (GWPs) relative to other greenhouse gases, so small atmospheric concentrations can have large effects on global temperatures. They can also have long atmospheric lifetimes--in some cases, lasting thousands of years. Like other long-lived greenhouse gases, fluorinated gases are well-mixed in the atmosphere, spreading around the world after they're emitted. Fluorinated gases are removed from the atmosphere only when they are destroyed by sunlight in the far upper atmosphere. In general, fluorinated gases are the most potent and longest lasting type of greenhouse gases emitted by human activities.

There are three main categories of fluorinated gases--hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). The largest sources of fluorinated gas emissions are described below.

  • Substitution for Ozone-Depleting Substances. Hydrofluorocarbons are used as refrigerants, aerosol propellants, solvents, and fire retardants. The major emissions source of these compounds is their use as refrigerants--for example, in air conditioning systems in both vehicles and buildings. These chemicals were developed as a replacement for chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) because they do not deplete the stratospheric ozone layer. Chlorofluorocarbons and HCFCs are being phased out under an international agreement, called the Montreal Protocol. Unfortunately, HFCs are potent greenhouse gases with long atmospheric lifetimes and high GWPs, and they are released into the atmosphere through leaks, servicing, and disposal of equipment in which they are used.
  • Industry. Perfluorocarbons are compounds produced as a by-product of various industrial processes associated with aluminum production and the manufacturing of semiconductors. Like HFCs, PFCs generally have long atmospheric lifetimes and high GWPs. Sulfur hexafluoride is used in magnesium processing and semiconductor manufacturing, as well as a tracer gas for leak detection. HFC-23 is produced as a by-product of HCFC-22 production.
  • Transmission and Distribution of Electricity. Sulfur hexafluoride is used in electrical transmission equipment, including circuit breakers. The GWP of SF6 is 23,900, making it the most potent greenhouse gases that the Intergovernmental Panel on Climate Change has evaluated.

To find out more about the role of fluorinated gases in warming the atmosphere, and their sources, visit the Causes of Climate Change page and the Greenhouse Gas Indicators page in the Science section.

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Overall, fluorinated gas emissions in the United States have increased by about 83% between 1990 and 2012. This increase has been driven by a 310% increase in emissions of hydrofluorocarbons (HFCs) since 1990 as they have been widely used as a substitute for ozone-depleting substances. Emissions of perfluorocarbons (PFCs) and sulfur hexafluoride (SF6) have actually declined during this time due to emission reduction efforts in the aluminum production industry (PFCs) and the electricity transmission and distribution industry (SF6).

Going forward, HFC emissions are projected to grow by nearly 140% between 2005 and 2020 as demands for refrigeration continue to grow and as more ozone-depleting substances are replaced. During this same period, emissions of SF6 are expected to decline by over 25%, while emissions of PFCs are projected to remain flat. Since the emissions from HFCs are far greater than the emissions of the other gases on a carbon dioxide-equivalence basis, substantial growth in emissions of F-gases is expected to continue. [1]

U.S. Fluorinated Gas Emissions, 1990-2012
Line graph that shows U.S. fluorinated gas emissions from 1990 to 2012. Fluorinated gas emissions have increased from approximately 90 million metric tons of carbon dioxide equivalents in 1990 to just above 150 million metric tons of carbon dioxide equivalents in 2008. The line shows a slight decline in 2009, followed by a sharp rebound in 2011 and 2012 to a high of just below 170 million metric tons.  It should be noted that the line does not increase uniformly, there are a few minor decreases in 2001 and 2003, but the overall trend is an increase in fluorinated gas emissions.

Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012.

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Reducing Fluorinated Gas Emissions

Because most fluorinated gases have a very long atmospheric lifetime, it will take many years to see a noticeable decline in current concentrations. However, there are a number of ways to reduce emissions of fluorinated gases, described below.

Examples of Reduction Opportunities for Fluorinated Gases
Emissions Source Examples of How Emissions Can be Reduced

Substitution of Ozone-Depleting Substances in Homes and Businesses

Refrigerants used by businesses and residences emit fluorinated gases. Emissions can be reduced by use of substitutes with lower global warming potentials and other technological improvements. Visit EPA's Ozone Layer Protection site to learn more about reduction opportunities in this sector.

Industry

Industrial users of fluorinated gases can reduce emissions by adopting fluorinated gas recycling and destruction processes, optimizing production to minimize emissions, and replacing these gases with alternatives. The following are EPA programs working to reduce these gases in the Industry sector:

Electricity Transmission and Distribution

Sulfur hexafluoride is an extremely potent greenhouse gas that is used for several purposes when transmitting electricity through the power grid. EPA is working with industry to reduce emissions through the SF6 Emission Reduction Partnership for Electric Power Systems which promotes leak detection and repair, use of recycling equipment, and employee training.

Transportation

Hydrofluorocarbons (HFCs) are released through the leakage of refrigerants used in vehicle air-conditioning systems. Leakage can be reduced through better system components, and through the use of alternative refrigerants with lower global warming potentials than those presently used. One important way the EPA is working to reduce HFC emissions is through its light-duty and heavy-duty vehicle standards.

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References

1. U.S. Department of State (2007). Projected Greenhouse Gas Emissions In: Fourth Climate Action Report to the UN Framework Convention on Climate Change . U.S. Department of State, Washington, DC, USA.

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